Respuesta :

Angle = arccos (dot product / product of the magnitues)


dot product = 1*-1 + 9*sqrt7 = 22.812

product of the magnitudes = sqrt(1 + 7) * sqrt(1 + 82) = 25.612


required angle = arccos (22.812/25.612) = 27 degrees to nearest degree


Its choice b.

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